The present invention relates generally to methods for treating harmful conditions and illnesses associated with abnormal vasculature.
Abnormal vasculature in a body is typically associated with a lesion. Lesions are generally defined as an abnormal tissue structure located in an organ or other body part, and are often a manifestation of a harmful condition, disease or illness. Lesions may take many specific forms, e.g., choroidal neovascularization (CNV) found in the eye, and tumors, both benign and malignant, located in organs and other parts of the body.
CNV is one manifestation of Age-Related Macular Degeneration (AMRD). AMRD is a leading cause of significant visual impairment in the elderly. CNV originates in the choroidal blood vessels of the eye which lie adjacent the retina. When a CNV forms, it may intrude into and displace a portion of the retina from its normal position, thereby distorting vision. Timely diagnosis and treatment of a CNV is an important therapeutic objective because permanent vision loss can result if hemorrhage of the CNV occurs.
Common methods of treating abnormal vasculature use laser technology. One example of such methods, used in the treatment of CNV, is photodynamic therapy (PDT). The object of PDT is to permit selective destruction of undesirable tissue without damaging surrounding healthy tissue. This is possible because the photodynamic dyes used in PDT are selectively retained in the area to be treated. For example, in the case of CNV, the photodynamic dye selectively binds to the proliferating endothelium in the CNV. Similarly, in the case of tumors, the photodynamic dye remains in cancer cells for a longer period of time than in normal, healthy cells. Thus, only a general identification of the tissue to be treated need be obtained before administering PDT.
Generally, the application of PDT requires the administration of a photodynamic dye into a subject, typically by IV injection. After the dye administration is completed, the dye becomes distributed throughout the body. The physician must then wait until the dye accumulates in the tissue to be treated, and the concentration of dye in the healthy tissues becomes relatively low compared to that in the tissue to be treated. When that point is reached, the dye in the tissue to be treated is subjected to radiation, e.g., light of a certain wavelength generated by a laser, causing excitation of the dye. While the precise mechanism is not fully understood, it is believed that the dye, when excited, generates oxygen radicals. These radicals attack the cells of the surrounding tissue, resulting in degranulation of those cells. By way of specific example, and in the case of a CNV, PDT destroys the endothelial cells of the CNV. This reduces, and preferably halts, the flow of blood within the CNV. In treating tumors, endoscopes are commonly used in combination with fiber optics to deliver radiation (in the form of light) of a particular wavelength (generally from about 630 nm to about 750 nm) to the tumor undergoing PDT. Radiation delivery via fiber optics is advantageous because it allows the treatment light source to be placed close to the tumor, enabling treatment of only one tumor. This delivery method is also currently required because the treatment radiation cannot pass through more than about 3 cm of tissue. One reference describing the use of PDT in cancer therapy is xe2x80x9cThe Use of PDT in Photodynamic Therapy in Oncology: Methods and Clinical Use,xe2x80x9d 85(6) J. Nat""l Cancer Inst. 443-456 (1993).
Unfortunately, PDT is not a permanent solution, particularly with respect to CNV treatment. Reperfusion following initially successful PDT on a CNV typically occurs within 4-12 weeks after treatment, requiring a subject to receive multiple retreatments. This on-going need for re-treatment is costly and inconvenient to the patient.
Further, and at least in the case of Photofrin(copyright) (a photodynamic dye used with PDT), patients experience a skin sensitivity to light after administration. More specifically, patients to whom Photofrin(copyright) has been administered must avoid direct sunlight for 4 to 6 weeks after administration, and take other related precautions, e.g., wear sunglasses and protective clothing when outdoors. In addition, surgery involving exposure of internal organs to bright surgical lights must be avoided.
A need thus exists for improved methods of treating conditions and illnesses having abnormal vasculature associated therewith, including, but not limited to, lesions, and, more specifically, CNVs and tumors.
The present invention meets the foregoing and other needs in a variety of ways. Generally, the present invention provides a method for treating a lesion, such as a CNV or tumor, in an animal. The methods of the present invention contemplate treating such a lesion by subjecting the lesion to PDT, and subjecting a blood vessel that carries blood into the lesion to thermal photocoagulation to reduce the flow of blood through that vessel and into the lesion. Regression of the lesion should follow this method of treatment.
It has been found methods of the present invention offer, among other benefits, enhanced therapeutic results and cost savings as compared to therapy consisting of PDT alone. For example, the need for PDT re-treatment is eliminated by the use of thermal photocoagulation, thereby lowering the overall cost of treatment and lessening patient inconvenience. Further, the undesirable side effects associated with PDT, e.g., skin sensitivity to light, are minimized using the inventive method.
More specifically, one aspect of the present invention includes, but is not limited to, the steps of: administering a first composition comprising a photodynamic dye and a pharmaceutically-acceptable carrier to the animal to fill at least a portion of the lesion with the first composition; applying radiation to the photodynamic dye in the lesion of a type and in an amount sufficient to excite the photodynamic dye; and applying radiation to the blood vessel that carries blood into the lesion of a type and in an amount sufficient to increase the temperature of the vessel, reducing the rate of blood flow through the vessel.
Another aspect of the present invention provides methods specific to the treatment of a CNV. In connection with the development of this aspect, it was recognized that, after PDT of a CNV was completed, and recurrence of the CNV was detected, angiograms of the CNV permitted CNV feeder vessels to be readily identified, as compared to angiograms obtained without prior PDT. Of course, once such feeder vessels are identified, thermal photocoagulation (with or without the use of a radiation-absorbing dye, the latter also referred to as dye enhanced thermal photocoagulation) can be performed with a relatively high degree of success, providing for relatively permanent treatment of the CNV.
A further aspect of the present invention provides methods specific to the treatment of a tumor in an animal. The method includes, but is not limited to, the steps of: administering a first composition comprising a photodynamic dye and a pharmaceutically-acceptable carrier to the animal to fill at least part of the tumor with the first composition; applying radiation to the photodynamic dye residing in the tumor of a type and in an amount sufficient to excite the photodynamic dye; and applying radiation to a blood vessel that carries blood into the tumor of a type and in an amount sufficient to increase the temperature of the vessel, reducing the rate of blood flow through the vessel and into the tumor.
All of the inventive aspects of the present invention as described and claimed herein may be used on animals, e.g., humans, dogs, cats, but are preferably used in connection with the diagnosis and treatment of human subjects.
The inventive methods may be expanded upon by the optional administration of other treatment steps or therapies. For example, and in connection with the treatment of tumors, the present invention may, if desired, be augmented by the administration of chemotherapeutic and/or anti-angiogenesis agents (either via IV or by direct injection into the tumor), conventional radiation therapy, or combinations thereof. If a tumor is undergoing treatment in accordance with the inventive methods, a decrease in size of the tumor after the treatment may permit successful removal of the tumor by surgery.
The foregoing and other aspects of the present invention will be more clearly understood upon reference to the following preferred embodiments.